(Partially) fix handling of type params depending on type params

If the first type parameter gets inferred, that's still not handled correctly;
it'll require some more refactoring: E.g. if we have `Thing<T, F=fn() -> T>` and
then instantiate `Thing<_>`, that gets turned into `Thing<_, fn() -> _>` before
the `_` is instantiated into a type variable -- so afterwards, we have two type
variables without any connection to each other.

1 files changed, 2 insertions, 2 deletions

diff --git a/crates/ra_hir_ty/src/db.rs b/crates/ra_hir_ty/src/db.rs
index 7889b8d2c..cad553273 100644
--- a/crates/ra_hir_ty/src/db.rs
+++ b/crates/ra_hir_ty/src/db.rs
@@ -14,7 +14,7 @@ use crate::{
     method_resolution::CrateImplDefs,
     traits::{chalk, AssocTyValue, Impl},
     Binders, CallableDef, GenericPredicate, InferenceResult, OpaqueTyId, PolyFnSig,
-    ReturnTypeImplTraits, Substs, TraitRef, Ty, TyDefId, TypeCtor, ValueTyDefId,
+    ReturnTypeImplTraits, TraitRef, Ty, TyDefId, TypeCtor, ValueTyDefId,
 };
 use hir_expand::name::Name;
 
@@ -65,7 +65,7 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
     fn generic_predicates(&self, def: GenericDefId) -> Arc<[Binders<GenericPredicate>]>;
 
     #[salsa::invoke(crate::lower::generic_defaults_query)]
-    fn generic_defaults(&self, def: GenericDefId) -> Substs;
+    fn generic_defaults(&self, def: GenericDefId) -> Arc<[Binders<Ty>]>;
 
     #[salsa::invoke(crate::method_resolution::CrateImplDefs::impls_in_crate_query)]
     fn impls_in_crate(&self, krate: CrateId) -> Arc<CrateImplDefs>;